Human device interfaces in particular for mobile devices often use sensors arrangements for detecting an user input that do not necessarily require any movable parts. Examples are touch screens and capacitive switches that are required to be touched to be activated. Such sensor systems comprise electrodes that are arranged on the device wherein if a user touches them or gets into very close proximity a change in capacitance can be measured to trigger an event. These electrodes are often formed by small metal plates, etched areas on a circuit board, or areas in a metal layer such as a transparent TIN oxide layer for use in displays.
Similar electrodes can also be used for electric field measurement. This type of sensor device allows detection of an object without touching and at far greater distances from the device as conventional capacitive sensor systems. In an electric field measurement system, an electrode is used as a transmitter to project an electric field outside or in front of a respective device. The field may be generated by a 30-200 kHz, in particular a 70-140 kHz or a 40-115 kHz, signal and thus is quasi-static in the near field. Whenever an object enters such an quasi-static electric field, its parameters are influenced or changed. The same electrode or a separate receiver electrode can be used to detect these changes. If a plurality of such electrodes are used in a sensing system, multi-dimensional gesture detection becomes possible which allows operation of the device without touching it. In electric field sensing arrangements the sensors often need to be shielded or arranged in specific order and then may be coupled to a front end integrated circuit device for evaluation of incoming signals.